Andrew Clarke, the founder of Cashrewards, the largest of the Australian cashback services, says last year US shoppers spent more than $US2 billion ($2.75 billion) on Cyber Monday alone, and this year it's expected to rise again.

Cashrewards has agreements with big name international and local retailers, including Saks Fifth Avenue, Forever 21 and Nike.

It will be the second-last Thanksgiving sales before the 10 per cent GST will be payable on all overseas online purchases from July 1, 2017.

At the moment, the GST is paid only on purchases of more than $1000.

While the discounts are attractive the Australian dollar is worth about 12 per cent less against the US dollar than a year ago – from about US85¢ to about US72¢ now.

Online shoppers should be mindful of shipping costs. There is no point buying something from overseas if the shipping costs amount to as much or more than the savings.

Remember that many local e-commerce sites could be running special deals at this time of year as well, though the big online sales day Click Frenzy has been and gone.

And do keep track of spending and do not spend more than you can afford.